1. Field of the Invention
The present invention relates to phthalocyanine compounds which can be employed as a dye for optical recording, a dye for color filter, and a material for use in photoelectric conversion device, electrophotographic photoconductor, organic semiconductor device, catalysts, gas sensor, and color filter.
2. Discussion of Background
Phathalocyanine compounds attract attention not only as conventionally employed pigments, but also as dyes for optical recording media, dyes for color filter, and materials for use in photoelectric conversion device, electrophotographic photoconductor, organic semiconductor device, catalysts, gas sensor, and color filter.
However, unsubstituted phthalocyanine compounds are slightly soluble or insoluble in most solvents and therefore considerably lack workability.
For instance, when a thin film of the unsubstituted phthalocyanine compound is formed for the above-mentioned applications, vacuum deposition or ultra fine particle dispersion method is generally employed. In either method, the productivity is extremely low. Thus, the slight solubility or insolubility in solvents of conventional phthalocyanine compounds is a great obstacle to the mass production of the above-mentioned media and devices.
In particular, when a phthalocyanine compound film prepared by vacuum deposition is used as a recording layer for an optical disk, it is necessary to perform crystal transformation of the recording layer into such a crystal form that is suitable for obtaining the recording characteristics required for the optical disk. This crystal transformation has to be conducted by heating the vacuum deposited phthalocyanine recording layer or exposing the vacuum deposited phthalocyanine recording layer to the vapor of an organic solvent for an extended period of time and the productivity of this method is significantly poor and therefore not used in practice for the production of optical disks.
With respect to optical disks, in particular, with compact disks, write once read many type compact disks have been actively developed in recent years. As organic dyes used as the materials for such write once read many type compact disks, cyanine dyes have been mainly used. Cyanine dyes are excellent in that they have large absorptivity coefficients, but have the shortcoming of not being light resistant. In order to eliminate this shortcoming, it has been proposed to add a photostabilizer such as a singlet oxygen quencher to the cyanine dyes. However, the addition of such a stabilizer is not sufficiently effective.
In sharp contrast to this, phthalocyanine dyes are comparable to the cyanine dyes and therefore the cyanine dyes can be replaced by phthalocyanine dyes with respect to the light absorption wavelength, and phthalocyanine dyes have high light resistance and therefore expected to find many applications in the field of recording materials. However, for such applications, the problem of phthalocyanine dyes that the solubilities thereof in organic solvents are extremely low has to be solved.
In order to solve this problem, it has been proposed to introduce some substituents into a phthalocyanine compound to improve the solubility thereof in organic solvents and use the phthalocyanine compound in the form of a coating liquid by dissolving the phthalocyanine compound in a solvent. For instance, in Japanese Laid-Open Patent Applications 1-180865, 2-265788 and 63-312888, there are disclosed phthalocyanine compounds with improved solubilities in organic solvents such as hydrocarbons with the introduction of an alkyl group, an alkoxyl group, or an alkylthio group in each benzene ring of phthalocyanine compounds.
Furthermore, it has been tried to introduce various functional groups such as ester group and polyether group into each benzene group of phthalocyanine dye compounds to increase the solubilities of phthalocyanine dye compounds in organic solvents.
However, when phthalocyanine compounds are used in a light absorption layer for an optical information recording medium, the phthalocyanine dye compounds have not only the problems of extremely low solubilities in organic solvents and poor workability, but also the problems that the absorptivity coefficients thereof on a longer wavelength side are lowered by the association of the molecules of the phthalocyanine dye compound in a superimposed manner when a film thereof is prepared because of the exceedingly high flatness of each phthalocyanine dye compound molecule, and that when used in write once read many type compact disks, with application of laser beams thereto, the recording sensitivity is not high due to the exceedingly high thermal stability of the phthalocyanine dye compounds.
The phthalocyanine dye compounds disclosed in the above-mentioned Japanese Patent Applications are improved with respect to the film formation properties, but the optical characteristics and thermal characteristics thereof are unsatisfactory and the above-mentioned problems have not yet been solved.